1. Technical Field
The present invention relates to a printing apparatus including a multi-function apparatus of a printer, a facsimile, and a copier executing printing on a printing medium.
2. Related Art
As an ink jet printer, there is known a serial type printer that reciprocates a carriage mounting a print head in a width direction intersecting a transport direction of a printing medium such as a printing sheet.
A serial type printer has a configuration in which the movement distance and the speed of the carriage is detected by allowing a detection sensor disposed in the carriage to read an encoder scale fixed to a printer main body and the print head is operated in synchronization with the detection result to obtain a high-quality image without dot position misalignment.
However, when sheet jamming or the like occurs during the operation of the printer, a user needs to take out the jammed sheet from the printer in person. At this time, when the hand of the user or the sheet comes into contact with the encoder scale, the scale position is changed. Therefore, a problem may arise in that the encoder scale may be deviated from an encoder slit of the detection sensor. When the encoder scale is deviated from the encoder slit, the movement motion of the carriage is not controlled, thereby causing breakdown.
In order to solve this problem, JP-A-9-277643 discloses the configuration in which a guide member engages so as to be pinched between both sides of the encoder scale in order to correct the relative position of the encoder scale relative to the detection sensor.
In recent years, printers have been used which are able to print an image on various kinds of printing media, such as a CR-R or a heavy sheet, different in size or thickness. When printing is executed on these printing media, the carriage is moved in a vertical direction so that the gap between the carriage and a platen is varied depending on the thickness of the printing media. In this case, since a lower portion of the encoder slit is opened and the encoder scale is fixed to a frame of the printer main body, the encoder scale may come out from the encoder slit more easily as the movement amount of the carriage is larger. That is, when a thick printing medium is used, the encoder scale may easily come out due to the increase in the movement amount of the carriage.
A configuration preventing the encoder scale from coming out may be taken into consideration by forming the encoder slit with a bag-like shape. However, in this configuration, it is necessary to ensure a slit space in the lower portion of the encoder scale to the degree that the slit space does not interrupt the encoder scale during the vertical movement motion of the carriage. However, since a transport roller holder that shaft-supports a transport roller transporting the printing medium is disposed in the lower portion of the encoder scale, it is difficult to ensure the slit space in the lower portion of the encoder scale.